Wind - Energy Policy Analysis: A Conceptual Framework - page 120

Figure 6.3 Wind Turbine

Rotor Blade

Gear Box

Nacelle

Wind

Generator

Power Cables

Tower Switchyard

Transformer

Source: Tennessee Valley Authority 2011.

In turbines, wind is used to turn blades, which rotate a shaft, which connects to a generator and
makes electricity, as illustrated in Figure 6.3. Modern wind turbines are based on two basic tech-
nologies: the familiar horizontal-axis variety and the less familiar vertical-axis design, like the
eggbeater-style Darrieus model, named after its French inventor (USDOE 2011b). Horizontal-axis
wind turbines typically have either two or three blades.
Utility-scale turbines range in size from 100 kilowatts to as large as several megawatts. A
typical commercial wind turbine may stand 390 feet above ground with blades 130 feet in diam-
eter (Nersesian 2010, 312). Large turbines are often grouped together into “wind farms,” which
provide bulk power to an interconnected electrical grid. After they are constructed, turbine towers
have relatively small footprints, and agricultural activities such as cultivating crops and grazing